“Yeah, there is a difference. He couldn’t be more naive as Baby Groot. I always think of the Groot that we saw on the first Guardians as a college-level Groot, so he’s not fully grown yet, but he’s a man. And once he sacrifices himself at the end of the movie, now he has to start all over, so to speak, but we’re gonna see this goofy, adorable, baby Groot thing running around the screen and just learning as he goes.”
SOURCE: Collider
